Fuel Cells Could Provide Clues to Spark of Life

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 The origins of life remains one of the greatest mysteries of science. But to simulate the primordial past—and the conditions that could have given rise to the spark of life—some scientists are turning to a technology usually associated with the car of the future: fuel cells.
 

 Their usefulness lies in their very basic similarity to biological cells: life forms need to store and use energy with chemical reactions that transfer electrons from one molecule to another. So in order for non-living materials, say rocks or minerals, to come alive, they would need to be able to perform this electron dance.
 
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/smoker.width-990_Vprgtrg.jpg"/>
<figcaption>Hydrothermal vents are one possible crucible for life on Earth.
 
 </figcaption>
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 A fuel cell fits this role nicely. Unlike a typical car engine, which combusts fuel like gasoline to convert the energy locked in chemical bonds into heat, a fuel cell takes fuel like hydrogen gas and oxygen and, with the help of electrodes and catalysts, produces electricity.
 

 Elizabeth Howell, writing for Universe Today:
 
<blockquote>

 When thinking of a car, the research team says, they point out that fuel cells create electrical energy through the reaction of fuels and oxidants. This is called a “redox reaction”, which takes place when a molecule loses electrons and another molecule gains them.
 
</blockquote>

 So where could early Earth have provided such conditions—both the raw minerals and also the electrical energy? Many scientists suspect hydrothermal vents. Howell:
 
<blockquote>

 Hydrothermal vents are hot geysers on the sea floor that are often considered an interesting spot for life studies. They host “extremophiles”, or forms of life that exist (“thrive” is the better word) despite a harsh environment. The researchers say these vents are a sort of “environmental fuel cell” because electrical energy is generated from redox reactions between seawater oxidants and hydrothermal vents.
 
</blockquote>

 This means fuel cells could mimic the conditions of hydrothermal vents within the four walls of a laboratory rather than in the ocean deep. The trick is to swap the normal platinum catalysts used to speed up the chemical reactions with iron and nickel, metals that would have been commonplace on early Earth. The iron-nickel catalyst is then placed in a tank and used to separate two reservoirs of seawater, one very hot and alkaline (like inside a vent), the other acidic and cool (like the seawater surrounding the vent). If the fuel cell still generates a current, then
 
 maybe
 
 life could form under those conditions.
 


 Et voila
 
 , some of the preliminary tests did generate electrical current. With more testing, they may be able to hone in on the chemistry that could have initiated primordial life and, eventually, all of us.
 
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 Learn more about the hydrothermal vent theory and other hypotheses about what sparked life in "Origins: How Life Began."
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 Photo credit:
 <a href="http://www.flickr.com/photos/38824354@N02/7377546868">
 Neptune Canada/Flickr (CC BY-NC-SA)
 </a>

Did Microbes Cause The Worst Mass Extinction Ever?

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 About 252 million years ago, Earth suffered the biggest mass extinction event in its history, known as the Great Dying. The atmosphere filled with carbon, the planet baked in a warmer climate, and the oceans acidified. When it was over, 90% of all species on the planet were extinct.
 

 Scientists have long blamed volcanoes for triggering this catastrophe by pumping the atmosphere full of greenhouse gases. But a team of scientists have identified a new suspect: life itself, in the form of microbes.
 
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/ocean-floor.width-990_tVXdwKF.jpg"/>
<figcaption>Microbial mats coated in white sulfate material on the ocean floor
 
 </figcaption>
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 In this scenario, microbes called methanogens evolved to gorge themselves on the organic remains of dying species, emitting methane as a byproduct. They pumped the atmosphere full of methane, raising the temperature and nearly wiping out life. The research, first presented by team leader Daniel Rothman at the annual conference of the American Geophysical Union in December 2012,
 <a href="http://www.pnas.org/content/early/2014/03/26/1318106111">
 was published online
 </a>
 this week in the Proceedings of the National Academy of Sciences.
 

 But although this scenario is plausible, it’s not airtight—the evidence is largely circumstantial.
 

 Rothman and his team first speculated that microbes were behind the Great Dying based on the speed at which heat-trapping carbon moved from the atmosphere into Earth’s oceans about 252 million years ago. Based on measurements from southern China and Austria, the team found it happened at an exponential rate. This, they argue, is the fingerprint of the exponential explosion of life, not volcanic activity. The carbon from volcanoes would have seeped into the ocean more gradually, slowing down as the ocean became saturated with carbon. But an exploding population of methane-producing organisms in the oceans could have kept belching the gas even after the oceans were saturated.
 

 There’s another piece of evidence: sometime within the last 500 million years, one class of methanogens, called
 
 Methanosarcina
 
 , evolved a new way to metabolize carbon in the form of acetate, a compound that would have been plentiful in ocean sediments littered with dead plants, animals, and microbes. The team analyzed the genomes of 50 methanogens, including direct descendants from the mutation as well as distant cousins, to pinpoint when the mutation occurred. By simulating gene mutation rates, they estimate the shift occurred 240 million years ago, give or take about 41 million years. That puts it at around the time of the Great Dying. It would have given the hungry microbes a new food source, allowing them to convert acetate into methane and furthering a vicious cycle where methane caused extinctions, deaths produced acetate, and microbes produced more methane. It’s a classic recipe for exponential growth.
 

 But methanogenic life needs more than just decomposing corpses—they also need nickel so their enzymes can fold into the right shape to perform their biological functions. The metal is scarce on the Earth’s surface, but volcanoes churn it up from deep in the planet. Rothman’s team also found a spike in nickel concentration in the geological record at a site in southern China right around when they think the microbes went into exponential overdrive. That led them to argue that volcanoes weren’t the main culprit, but that they served as a catalyst, providing the raw biological material that allowed
 
 Methanosarcina
 
 to flourish.
 

 This picture fits together, but not everyone thinks it’s a better explanation.
 

<a href="http://www.nature.com/news/archaeageddon-how-gas-belching-microbes-could-have-caused-mass-extinction-1.14958">
 Chelsea Wald writing for Nature
 </a>
 :
 
<blockquote>

 Some scientists are not so quick to relegate the volcanoes to a supporting role, however. What the researchers have found is part of the connection between the volcanoes and the die-out, says palaeobiologist Douglas Erwin of the Smithsonian National Museum of Natural History in Washington DC. But he warns that the evidence is “hardly conclusive”.
 
</blockquote>

 And not all of the details are nailed down. Rothman’s team thinks the nickel they see in south China came from Siberian volcanoes, the ones that most scientists think caused the mass extinction in the first place. But Marc Reichow at the University of Leicester is skeptical, reports
 <a href="http://theconversation.com/the-greatest-mass-extinction-ever-may-have-been-kicked-off-by-microbes-25061">
 Akshat Rathi for The Conversation
 </a>
 :
 
<blockquote>

 He argues that there is no evidence that the increased nickel came from Siberian volcanoes. Rothman agrees that current data cannot identify the source of the nickel. “This is an interesting hypothesis, but I think that Great Dying was the doing of many ‘kill mechanisms’ rather than just a single mechanism suggested here,” Reichow said.
 
</blockquote>

 What
 
 is
 
 clear is that microscopic life can have enormous consequences across the entire planet. After all, if bacteria hadn’t evolved the ability to perform photosynthesis 2.5 billion years ago, pumping the Earth’s atmosphere full of oxygen, we—and the rest of the animal kingdom—wouldn’t be here today.
 

 In the 1970s, scientist James Lovelock proposed the famous Gaia hypothesis—that life modifies its environment to suit itself, like a self-sustaining superorganism. Rothman’s theory could serve as an example of an anti-Gaian theory, or what paleontologist Peter Ward calls
 <a href="http://blogs.scientificamerican.com/observations/2010/01/13/paleontologist-peter-wards-medea-hypothesis-life-is-out-to-get-you/">
 the Medea hypothesis
 </a>
 —that life is ultimately suicidal and kills itself off. For now, at least as far as Rothman and colleagues’ findings are concerned, the jury is still out.
 
</section>

<a href="http://oceanexplorer.noaa.gov/explorations/12fire/background/microbio/media/mat_meadow.html">
 NOAA
 </a>

The Hacker Who Exposed South Korea's Deadly Epidemic

Out of Africa—And Back Again?

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 Every person on the planet can trace their genetic roots to Africa, the source of the great migration of humanity that began some 60,000 years ago. But it turns out that one group may have staged an epic return trek, erased by the sands of time and lost to human memory—until now.
 

 Scientists have uncovered their journey in a new study of the genome of the Khoisan tribes at the southern tip of Africa. Originally, the group of hunter-gatherers and herders was thought to be merely reclusive, having been isolated for tens of thousands of years. But the new research shows they actually share DNA with people from modern-day Spain and Italy. In other words, these African tribes are actually part European.
 
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<img alt="san hunters" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/san-hunters.width-990_tZGGntI.jpg"/>
<figcaption>These Khoisan hunter-gatherers may trace some of their ancestry back to southern Europe, according to a new genetic analysis.
 
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 The team also found a similar genetic signal in East Africa, beginning roughly 3,000 years ago. Combined with linguistic and archaeological evidence, they propose the following scenario:
 

 The Khoisan’s European ancestors were herders who began their return journey by settling in East Africa. This lines up with historical accounts like the Biblical kingdom of Sheba and the archaeological record of the kingdom of D’mt in what is now Ethiopia. Then, according to the genetic analysis, some of them pushed further south, down to the ends of the continent, 900–1800 years ago, introducing their pastoral practices to the local hunter-gatherer tribes.
 

 The Khoisan’s new origin story, published this week
 <a href="http://www.pnas.org/content/early/2014/01/29/1313787111.abstract">
 in the online edition
 </a>
 of Proceedings of the National Academy of Sciences, illustrates that human migrations may be more common than recorded history suggests.
 

 Catherine Brahic, writing for New Scientist:
 
<blockquote>

 “These populations were always thought to be pristine hunter-gatherers who had not interacted with anyone for millennia,” says [team member and] linguist Brigitte Pakendorf of the University of Lyon in France. “Well, no. Just like the rest of the world, Africa had population movements too. There was simply no writing, no Romans or Greeks to document it.”
 
</blockquote>

 Brahic also points out that the study may also change our understanding of some much more distant ancestors: Neanderthals. We know that the human masses migrating from Africa mingled with Neanderthals, spreading traces of Neanderthal DNA around the world. But if some groups later migrated back to Africa, Neanderthal DNA could be widespread
 
 within
 
 the continent, as well.
 
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 Learn more about the Neanderthal genome in "Decoding Neanderthals."
 </div>
</section>

 Photo credit:
 <a href="www.flickr.com/photos/charlesfred/2124785568/in/photostream/">
 Charles Roffey/Flickr (CC BY-NC-SA 2.0)
 </a>

An artist's rendition of Sedna, discovered in 2003

New Icy Body Hints at Planet Lurking Beyond Pluto

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 In 2003, Caltech astronomer Mike Brown and his team discovered a new addition to the solar system: a small icy world called Sedna. It was a bit of an oddball—taking an extremely elongated orbit that sent it well beyond Neptune—but astronomers suspected it wasn’t alone.


 After over a decade of searching, Sedna finally has a friend. Yesterday, astronomers announced they’ve found a similar body—dubbed a sednoid after the original finding—in the same neighborhood. The discovery,
 <a href="http://www.nature.com/nature/journal/v507/n7493/full/nature13156.html">
 published in Nature,
 </a>
 suggests the so-called inner Oort cloud may be real. The inner Oort cloud sits outside the Kuiper belt, which lies just beyond Neptune’s orbit, but inside the outer Oort cloud. All three of these regions are filled with swarms of ice balls smaller than our moon.


 Also striking were the similar orbits of the two sednoids, which are reviving speculation that there may be a much bigger, unseen planet lurking in the outer reaches of our solar system.


 The new sednoid, called 2012 VP113, was discovered by Chadwick A. Trujillo and Scott Sheppard of the Gemini Observatory in Hawaii. Its closest approach to the sun is 7.4 billion miles, which is 80 times farther than Earth’s proximity. The team estimates it’s about 450 kilometers in diameter—probably large enough and round enough to be considered a dwarf planet.


 Finding 2012 VP113 is especially sweet for Trujillo, who was on the team that discovered Sedna. “It’s really satisfying to see that we were right and there is a whole huge population of bodies like Sedna,” Trujillo says. “2012 VP113 is the smoking gun” that confirms the inner Oort cloud, says Meg Schwamb, an astronomer at Academia Sinica in Taipei who searched for sednoids with Brown during her PhD.

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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/image1.width-990_IBtreUK.jpg"/>
<figcaption>In this diagram, Sedna's orbit is shown in orange and 2012 VP113's orbit is shown in red. The dotted lines are the Kuiper belt, and the solid lines are the orbits of Jupiter, Saturn, Uranus, and Neptune.
 
 </figcaption>
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 The orbits of both Sedna and 2012 VP113 are oriented away from the plane of the other planets at a suspiciously similar angle. It could just be coincidence, but it could also hint at a massive planet many times the size of Earth hiding in the inner Oort cloud whose gravity shepherds sednoids into similar orbits.


 We’ve been there before. Astronomers have invoked the idea of a so-called “Planet X” in the outer solar system many times and for different reasons, dating back to the mid–1800s when American astronomer Percival Lowell became convinced that an unseen planet was causing disturbances in the orbits of Uranus and Neptune. For a few decades, astronomers thought Pluto fit the bill, but in 1978 they learned it was too small to cause the disturbances. Then, in 1992, NASA’s Voyager revealed that Neptune was slightly more massive than previously thought, explaining the planet’s orbit.

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 Scientists have also toyed with the idea of an unseen body to explain the dynamics of comets. In 1984, physicist Richard Muller suggested that a small star roughly one light year away could be tugging on comets, tossing them into the inner solar system and causing periodic mass extinctions. That idea fizzled when paleontologists found out that comet-caused extinctions weren’t as regular as they’d thought. (That didn’t stop
 <a href="http://www.pbs.org/wgbh/nova/next/tech/big-data-shows-how-conspiracy-theories-emerge-on-facebook/">
 conspiracy theorists
 </a>
 from convincing themselves that not only did such a planet exist, but NASA was covering up
 <a href="http://en.wikipedia.org/wiki/Nibiru_cataclysm">
 an impending cataclysmic collision
 </a>
 .)


 Still, most comets seem to come from the outer Oort cloud, so astronomers kept around the idea of a small star or a gas giant to explain it.


 Just two weeks ago, that hypothesis took a huge blow. Kevin Luhman, a Penn State astronomer, announced that NASA’s Wide-Field Infrared Survey Explorer hadn’t turned up anything like it.


 So if a gas planet isn’t there, what could explain the similar orbits of Sedna and 2012 VP113? Perhaps, say Trujillo and Shepherd, an unseen rocky super Earth could be the cause. “It would be too small and too faint to be detected by WISE, so it is plausible that it exists,” Luhman says.


 Trujillo and Sheppard simulated the presence of a super Earth some 23 billion miles from the sun, and their results suggest the super Earth hypothesis is valid. But no telescope is powerful enough to detect such a planet out there. Ramon Brasser, who studies the outer solar system at Acadmia Sinica, doesn’t think there’s a super Earth out beyond Neptune, calling it “a low-probability event.”

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 Schwamb says “the jury is still out” on this latest revival of a Planet X. The same goes for a lot of what we know about the Oort cloud. She compares our understanding of it today to what we knew about the Kuiper belt in 1992, when astronomers had just discovered the second object out there. (Pluto was the first.) “I think we’re just at the beginning of learning about this region,” she says.


 Planet X would explain why the angles of Sedna and 2013 VP113’s orbits are similar, but it doesn’t explain how they ended up in the inner Oort cloud in the first place. The most accepted theory suggests that they started out as comets that were boosted into higher orbits when the sun came close to another star.


 While that’s unlikely in our rather sparse sector of space, there are a couple of ways this could happen. Our sun—like most every star—was born from a cloud of gas that spawned a cluster of swirling stars. In those early years, close encounters would have been common. Or at another point in its distant past, the sun may have been traversing more crowded parts of the galaxy.


 2012 VP113 doesn’t settle this debate. “We really need to find several more of these objects to say anything significant,” Sheppard says. Astronomers are hoping a new generation of telescopes with wide fields of view—like the upcoming
 <a href="http://www.lsst.org/lsst/">
 Large Synoptic Survey Telescope
 </a>
 —will speed up the search.


 Photo credits: NASA/JPL-Caltech, Scott S. Sheppard: Carnegie Institution for Science

The similar orbits of the two icy bodies are reviving speculation that there may be a big, unseen planet lurking in the outer reaches of our solar system.

Chemists Hack Blu-ray Players to Test for Salmonella and Parasites

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 The Blu-ray player under your TV isn’t just for playing movies—it can also test your food and water to see if it’s safe.
 

 A team of researchers in Spain have taken off-the-shelf Blu-ray players and discs and, with a little hacking, turned them into cheap medical screening devices to detect dangerous bacteria and parasites. The disc acts as the platform for the sample, and the laser scans the samples. The team reports that it’s just as accurate as conventional lab equipment at a fraction of the cost and size, meaning health workers could take them into remote areas to test water supplies and monitor the environment.
 
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<figcaption>With a little modification, Blu-ray players can be a cheap and effective clinical testing device.
 
 </figcaption>
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 Normally, a Blu-ray player works by using its 405-nm laser to read the microscopic pits that make up the digital ones and zeros of the disc’s data. But the team installed a custom data board to read out an analog signal that measures the reflectivity of the disc.
 

 The discs were prepared by attaching bits of DNA or pieces of protein, known as probes, to the surface of the disc and recorded which bit was placed where on the disc. The probes work by snagging certain complementary strands or compounds from the test solution. To test a sample, they ran the solution containing the pathogen’s DNA or microcystin, a toxic produced by certain bacteria, over the data side of a Blu-ray disc. When they washed off the excess solution, the DNA or toxin remains stuck to the appropriate probes. The researchers then popped the disc in the drive and spun it up. The laser scans the disc, building a high-resolution image. The team then analyzes the image to see which probes attracted which DNA strand or compound.
 

 So far, they’ve tested the method with two types of bacteria:
 
 Salmonella typhimuium,
 
 and an intestinal parasite known as
 
 Cronobacter sakazakii
 
 . It also worked with microcystins, a biotoxin created by cyanobacteria that can infect drinking water and cause gastrointestinal unpleasantness and allergic reactions.
 

 Perhaps surprisingly, using optical discs as life science laboratory instruments isn’t new. Here’s Sergi Morais, one of the project’s team members, being interviewed by Matthew Peach of Optics.org:
 
<blockquote>

 “Our team has been working with this type of technology for 10 years. We started working with regular CDs then DVDs. Then we realized that Blu-ray was even more sensitive than the previous formats.”
 
</blockquote>

 There are a couple reasons why the Blu-ray format, which was introduced to accommodate HD video, works better as a medical screening device.
 

 First, the coating on Blu-ray discs is extremely hydrophobic, which means it repels water. So when researchers apply sample drops to the surface, they tend to stay bunched up in a sphere instead of spreading out across the surface. That means they can fit more samples onto a single disc, and it also improves the quality of the laser’s data. Second, the laws of physics allow Blu-ray’s blue lasers to be focused to a smaller area than the red lasers in DVD players; this is why we can cram more data onto a Blu-ray disc, and it also means the researchers can get clearer images of the sample drops. Together, these features make Blu-ray players several times more accurate than DVD players for this kind of testing.
 
</section>

 Photo credit:
 <a href="http://www.flickr.com/photos/pitzyper/2930196202/">
 Diego Correa/Flickr (CC BY)
 </a>

This “Energy Ribbon” is Helping Astronomers Map the Solar System’s Frontier

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 The outer fringes of the solar system are a bit like the Wild West—it’s a region of space where the long arm of the sun’s magnetic field weakens and the outside galaxy begins to assert its dominion. We don’t know much about what happens here, or what the interstellar magnetic field is like.
 

 We can see evidence of the power struggle between interstellar space and our solar system in the form of a mysterious “energy ribbon” of particles, which astronomers are using to determine what, exactly, is going on out there. From what we can see, it’s looking like the forces of the galaxy may hold more sway over our corner of space than we thought.
 
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/energy-ribbon-16x9.width-990_jXmy4st.jpg"/>
<figcaption>A visualization of the energy ribbon as seen from NASA's IBEX spacecraft
 
 </figcaption>
</figure>

 Scientists only discovered the ribbon in 2009, thanks to NASA’s Interstellar Boundary Explorer (IBEX) spacecraft, which orbits Earth but looks out to the edge of the solar system. The ribbon is made up of particles that come from the heliopause, the boundary where the influence of the sun’s magnetic field bumps up against the interstellar medium.
 

 David McComas, the principal investigator for the IBEX spacecraft,
 <a href="http://www.pbs.org/wgbh/nova/next/space/voyager-ibex-and-the-edge-of-the-solar-system/">
 wrote for NOVA Next last April
 </a>
 about the heliopause:
 
<blockquote>

 When the magnetic fields of the solar wind hit the magnetic fields of the interstellar medium, they do not intermix. The expanding solar wind pushes against the interstellar medium, clearing out a cavity in interstellar space known as the heliosphere. The boundary of that bubble is where the solar wind’s strength exactly matches the pressure of the interstellar medium. We call it the heliopause, and it’s often considered to be the very outer edge of our solar system.
 
</blockquote>

 Here, particles entering and exiting the solar system mingle and exchange electrons. This bartering creates rogue particles that have no electric charge, meaning they fly through space without being deflected by any magnetic field.
 

 But IBEX suggested that these neutral particles from the energy ribbon still retained an imprint of loyalty—the direction they travel in is actually aligned to the outside, interstellar magnetic field. Now, scientists are beginning to confirm this picture. A team led by Nathan Schwadron of the University of New Hampshire compared the IBEX measurements to ground-based observations of cosmic rays, another indicator of the interstellar magnetic field.
 

 These mysterious particles are thought to be survivors of ancient stellar explosions and close encounters with distant galactic cores, and they ride into the solar system packing a lot more energy than the neutral ones. They also have an electric charge, which means they are followers of the galaxy’s magnetic field. And when Schwadron’s team compared a map of them to one they derived from the IBEX data, they looked very similar, offering an independent confirmation that the energy ribbon is aligned with the galaxy’s magnetic field. “That was something we were completely lacking,” he told me. It suggests that the galaxy exerts more influence in our solar system’s border regions than previously suspected, warping the entire heliosphere.
 

 There is, however, one well-known spacecraft that has yet to join this consensus: Voyager 1. NASA declared that the craft left the solar system in September 2013, which means it should be measuring the interstellar magnetic field without interference from the sun. But strangely, Voyager 1’s galactic compass is pointing in a much different direction than the one that Schwadron’s team determined from the IBEX data.
 

 Elizabeth Howell, writing for Space.com:
 
<blockquote>

 The
 <a href="http://www.space.com/17456-voyager-1-spacecraft-solar-system-edge.html">
 few studies examining this issue
 </a>
 show little consensus. An October paper co-authored by Schwadron in Astrophysical Journal Letters argued that Voyager 1 could be measuring interstellar plasma coming in through magnetic field lines, but may still be in the heliosheath itself. This stands in contrast to findings from NASA and other science groups saying Voyager 1 is
 <a href="http://www.space.com/22797-voyager-1-interstellar-space-nasa-proof.html">
 definitively in interstellar space
 </a>
 .
 

 The researchers noted that Voyager 1 is picking up its information “at a specific time and place”, but IBEX’s data is collected and averaged across vast distances, so that could also lead to discrepancies.
 
</blockquote>

 It’s further evidence that Voyager 1 never crossed a hard border when it “left the solar system.” Instead, it’s traversing a very chaotic region of space, where the laws of physics remain, if not suspended, at least poorly understood.
 
</section>

 Photo credit: NASA

Mark Zastrow

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